A year later, the ship sank and the crew were brought onshore in Somalia. Two sailors subsequently died of illnesses.

Mr Balbero told the BBC that the last four and a half years had left him and his compatriots “like walking dead”.

Asked how the pirates treated them, he said: “They give us small amount of water only… We eat rat. Yes, we cook it in the forest.”

“[We] just eat anything, anything. You feel hungry, you eat.”

He also spoke of their difficulties adjusting to life after their ordeal, saying: “I don’t know what is… outside of this world when this finish, so it’s very hard to start again.”

The group are believed to be some of the last remaining captives held by Somali pirates, after a wave of hijackings in the mid-2000s.

Piracy off the coast of Somalia, usually for ransom, has reduced significantly in recent years, in part because of extensive international military patrols of the most vulnerable areas.

Separately a clip has emerged of the survivors, which appeared to have been taken in 2014 by the pirates amid negotiations as proof that the hostages were still alive.

The clip, released by a Taiwanese lawmaker who took part in the negotiations, shows the group of men looking thin and haggard and surrounded by masked gunmen.

It then cuts to a man identified by Taiwanese media as Shen Jui-chang, the Taiwanese chief engineer of the hijacked ship.

In the clip, Mr Shen says in Mandarin that the men were only given a litre of water a day to drink despite the heat. “There is no water, there is no food,” he said, adding that “every one of us has some kind of illness”.

“The pirates won’t get medicine for you, they say that they don’t have money to buy medicine. That’s how two young men have already died for nothing,” he says.

Taiwan’s foreign affairs ministry said the men were freed after a ransom was paid by the ship’s owner as well as groups contracted to negotiate with the pirates, Taiwanese media reported.